Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.112
1.1 deraadt 1: /*
1.39 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
5: * Code to connect to a remote host, and to perform the client side of the
6: * login (authentication) dialog.
1.78 deraadt 7: *
8: * As far as I am concerned, the code I have written for this software
9: * can be used freely for any purpose. Any derived versions of this
10: * software must be clearly marked as such, and if the derived work is
11: * incompatible with the protocol description in the RFC file, it must be
12: * called by a name other than "ssh" or "Secure Shell".
1.39 deraadt 13: */
1.1 deraadt 14:
15: #include "includes.h"
1.112 ! markus 16: RCSID("$OpenBSD: sshconnect.c,v 1.111 2001/10/01 21:51:16 markus Exp $");
1.1 deraadt 17:
1.66 markus 18: #include <openssl/bn.h>
1.71 markus 19:
1.91 markus 20: #include "ssh.h"
1.1 deraadt 21: #include "xmalloc.h"
22: #include "rsa.h"
1.59 markus 23: #include "buffer.h"
1.1 deraadt 24: #include "packet.h"
25: #include "uidswap.h"
1.21 markus 26: #include "compat.h"
1.58 markus 27: #include "key.h"
1.71 markus 28: #include "sshconnect.h"
1.58 markus 29: #include "hostfile.h"
1.91 markus 30: #include "log.h"
31: #include "readconf.h"
32: #include "atomicio.h"
33: #include "misc.h"
1.51 markus 34:
1.70 markus 35: char *client_version_string = NULL;
36: char *server_version_string = NULL;
1.59 markus 37:
1.43 markus 38: extern Options options;
1.50 markus 39: extern char *__progname;
1.91 markus 40:
41: /* AF_UNSPEC or AF_INET or AF_INET6 */
42: extern int IPv4or6;
1.43 markus 43:
1.110 markus 44: static const char *
45: sockaddr_ntop(struct sockaddr *sa)
46: {
47: void *addr;
48: static char addrbuf[INET6_ADDRSTRLEN];
49:
50: switch (sa->sa_family) {
51: case AF_INET:
52: addr = &((struct sockaddr_in *)sa)->sin_addr;
53: break;
54: case AF_INET6:
55: addr = &((struct sockaddr_in6 *)sa)->sin6_addr;
56: break;
57: default:
58: /* This case should be protected against elsewhere */
59: abort();
60: }
61: inet_ntop(sa->sa_family, addr, addrbuf, sizeof(addrbuf));
62: return addrbuf;
63: }
64:
1.39 deraadt 65: /*
66: * Connect to the given ssh server using a proxy command.
67: */
1.109 itojun 68: static int
1.103 markus 69: ssh_proxy_connect(const char *host, u_short port, struct passwd *pw,
1.3 provos 70: const char *proxy_command)
1.1 deraadt 71: {
1.38 markus 72: Buffer command;
73: const char *cp;
74: char *command_string;
75: int pin[2], pout[2];
1.69 deraadt 76: pid_t pid;
1.49 markus 77: char strport[NI_MAXSERV];
1.38 markus 78:
79: /* Convert the port number into a string. */
1.49 markus 80: snprintf(strport, sizeof strport, "%hu", port);
1.38 markus 81:
82: /* Build the final command string in the buffer by making the
83: appropriate substitutions to the given proxy command. */
84: buffer_init(&command);
85: for (cp = proxy_command; *cp; cp++) {
86: if (cp[0] == '%' && cp[1] == '%') {
87: buffer_append(&command, "%", 1);
88: cp++;
89: continue;
90: }
91: if (cp[0] == '%' && cp[1] == 'h') {
92: buffer_append(&command, host, strlen(host));
93: cp++;
94: continue;
95: }
96: if (cp[0] == '%' && cp[1] == 'p') {
1.49 markus 97: buffer_append(&command, strport, strlen(strport));
1.38 markus 98: cp++;
99: continue;
100: }
101: buffer_append(&command, cp, 1);
102: }
103: buffer_append(&command, "\0", 1);
104:
105: /* Get the final command string. */
106: command_string = buffer_ptr(&command);
107:
108: /* Create pipes for communicating with the proxy. */
109: if (pipe(pin) < 0 || pipe(pout) < 0)
110: fatal("Could not create pipes to communicate with the proxy: %.100s",
111: strerror(errno));
112:
113: debug("Executing proxy command: %.500s", command_string);
114:
115: /* Fork and execute the proxy command. */
116: if ((pid = fork()) == 0) {
117: char *argv[10];
118:
119: /* Child. Permanently give up superuser privileges. */
1.103 markus 120: permanently_set_uid(pw);
1.38 markus 121:
122: /* Redirect stdin and stdout. */
123: close(pin[1]);
124: if (pin[0] != 0) {
125: if (dup2(pin[0], 0) < 0)
126: perror("dup2 stdin");
127: close(pin[0]);
128: }
129: close(pout[0]);
130: if (dup2(pout[1], 1) < 0)
131: perror("dup2 stdout");
132: /* Cannot be 1 because pin allocated two descriptors. */
133: close(pout[1]);
134:
135: /* Stderr is left as it is so that error messages get
136: printed on the user's terminal. */
1.89 markus 137: argv[0] = _PATH_BSHELL;
1.38 markus 138: argv[1] = "-c";
139: argv[2] = command_string;
140: argv[3] = NULL;
141:
142: /* Execute the proxy command. Note that we gave up any
143: extra privileges above. */
1.89 markus 144: execv(argv[0], argv);
145: perror(argv[0]);
1.38 markus 146: exit(1);
147: }
148: /* Parent. */
149: if (pid < 0)
150: fatal("fork failed: %.100s", strerror(errno));
151:
152: /* Close child side of the descriptors. */
153: close(pin[0]);
154: close(pout[1]);
155:
156: /* Free the command name. */
157: buffer_free(&command);
158:
159: /* Set the connection file descriptors. */
160: packet_set_connection(pout[0], pin[1]);
1.1 deraadt 161:
1.110 markus 162: /* Indicate OK return */
163: return 0;
1.1 deraadt 164: }
165:
1.39 deraadt 166: /*
167: * Creates a (possibly privileged) socket for use as the ssh connection.
168: */
1.109 itojun 169: static int
1.103 markus 170: ssh_create_socket(struct passwd *pw, int privileged, int family)
1.1 deraadt 171: {
1.105 markus 172: int sock, gaierr;
173: struct addrinfo hints, *res;
1.1 deraadt 174:
1.40 markus 175: /*
176: * If we are running as root and want to connect to a privileged
177: * port, bind our own socket to a privileged port.
178: */
1.38 markus 179: if (privileged) {
180: int p = IPPORT_RESERVED - 1;
1.49 markus 181: sock = rresvport_af(&p, family);
1.38 markus 182: if (sock < 0)
1.55 markus 183: error("rresvport: af=%d %.100s", family, strerror(errno));
184: else
185: debug("Allocated local port %d.", p);
1.105 markus 186: return sock;
187: }
188: /*
189: * Just create an ordinary socket on arbitrary port. We use
190: * the user's uid to create the socket.
191: */
192: temporarily_use_uid(pw);
193: sock = socket(family, SOCK_STREAM, 0);
194: if (sock < 0)
195: error("socket: %.100s", strerror(errno));
196: restore_uid();
197:
198: /* Bind the socket to an alternative local IP address */
199: if (options.bind_address == NULL)
200: return sock;
201:
202: memset(&hints, 0, sizeof(hints));
203: hints.ai_family = IPv4or6;
204: hints.ai_socktype = SOCK_STREAM;
205: hints.ai_flags = AI_PASSIVE;
206: gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
207: if (gaierr) {
208: error("getaddrinfo: %s: %s", options.bind_address,
209: gai_strerror(gaierr));
210: close(sock);
211: return -1;
212: }
213: if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
214: error("bind: %s: %s", options.bind_address, strerror(errno));
215: close(sock);
216: freeaddrinfo(res);
217: return -1;
1.38 markus 218: }
1.105 markus 219: freeaddrinfo(res);
1.38 markus 220: return sock;
1.1 deraadt 221: }
222:
1.39 deraadt 223: /*
1.49 markus 224: * Opens a TCP/IP connection to the remote server on the given host.
225: * The address of the remote host will be returned in hostaddr.
226: * If port is 0, the default port will be used. If anonymous is zero,
1.39 deraadt 227: * a privileged port will be allocated to make the connection.
228: * This requires super-user privileges if anonymous is false.
229: * Connection_attempts specifies the maximum number of tries (one per
230: * second). If proxy_command is non-NULL, it specifies the command (with %h
231: * and %p substituted for host and port, respectively) to use to contact
232: * the daemon.
1.110 markus 233: * Return values:
234: * 0 for OK
235: * ECONNREFUSED if we got a "Connection Refused" by the peer on any address
236: * ECONNABORTED if we failed without a "Connection refused"
237: * Suitable error messages for the connection failure will already have been
238: * printed.
1.39 deraadt 239: */
1.38 markus 240: int
1.49 markus 241: ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
1.41 markus 242: u_short port, int connection_attempts,
1.103 markus 243: int anonymous, struct passwd *pw,
1.38 markus 244: const char *proxy_command)
1.1 deraadt 245: {
1.90 markus 246: int gaierr;
247: int on = 1;
1.49 markus 248: int sock = -1, attempt;
1.90 markus 249: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.49 markus 250: struct addrinfo hints, *ai, *aitop;
1.38 markus 251: struct linger linger;
1.90 markus 252: struct servent *sp;
1.110 markus 253: /*
254: * Did we get only other errors than "Connection refused" (which
255: * should block fallback to rsh and similar), or did we get at least
256: * one "Connection refused"?
257: */
258: int full_failure = 1;
1.38 markus 259:
1.77 deraadt 260: debug("ssh_connect: getuid %u geteuid %u anon %d",
261: (u_int) getuid(), (u_int) geteuid(), anonymous);
1.38 markus 262:
263: /* Get default port if port has not been set. */
264: if (port == 0) {
265: sp = getservbyname(SSH_SERVICE_NAME, "tcp");
266: if (sp)
267: port = ntohs(sp->s_port);
268: else
269: port = SSH_DEFAULT_PORT;
270: }
271: /* If a proxy command is given, connect using it. */
272: if (proxy_command != NULL)
1.103 markus 273: return ssh_proxy_connect(host, port, pw, proxy_command);
1.38 markus 274:
275: /* No proxy command. */
276:
1.49 markus 277: memset(&hints, 0, sizeof(hints));
278: hints.ai_family = IPv4or6;
279: hints.ai_socktype = SOCK_STREAM;
280: snprintf(strport, sizeof strport, "%d", port);
281: if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
1.50 markus 282: fatal("%s: %.100s: %s", __progname, host,
283: gai_strerror(gaierr));
1.38 markus 284:
1.46 markus 285: /*
286: * Try to connect several times. On some machines, the first time
287: * will sometimes fail. In general socket code appears to behave
288: * quite magically on many machines.
1.110 markus 289: */
290: for (attempt = 0; ;) {
1.38 markus 291: if (attempt > 0)
292: debug("Trying again...");
293:
1.49 markus 294: /* Loop through addresses for this host, and try each one in
1.68 markus 295: sequence until the connection succeeds. */
1.49 markus 296: for (ai = aitop; ai; ai = ai->ai_next) {
297: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
298: continue;
299: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
300: ntop, sizeof(ntop), strport, sizeof(strport),
301: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
302: error("ssh_connect: getnameinfo failed");
303: continue;
304: }
305: debug("Connecting to %.200s [%.100s] port %s.",
306: host, ntop, strport);
307:
308: /* Create a socket for connecting. */
1.103 markus 309: sock = ssh_create_socket(pw,
1.80 markus 310: !anonymous && geteuid() == 0,
1.49 markus 311: ai->ai_family);
312: if (sock < 0)
1.110 markus 313: /* Any error is already output */
1.49 markus 314: continue;
315:
316: /* Connect to the host. We use the user's uid in the
317: * hope that it will help with tcp_wrappers showing
318: * the remote uid as root.
1.40 markus 319: */
1.103 markus 320: temporarily_use_uid(pw);
1.49 markus 321: if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) {
322: /* Successful connection. */
1.102 markus 323: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 324: restore_uid();
325: break;
1.49 markus 326: } else {
1.110 markus 327: if (errno == ECONNREFUSED)
328: full_failure = 0;
329: log("ssh: connect to address %s port %s: %s",
330: sockaddr_ntop(ai->ai_addr), strport,
331: strerror(errno));
1.38 markus 332: restore_uid();
1.40 markus 333: /*
334: * Close the failed socket; there appear to
335: * be some problems when reusing a socket for
336: * which connect() has already returned an
337: * error.
338: */
1.38 markus 339: shutdown(sock, SHUT_RDWR);
340: close(sock);
341: }
342: }
1.49 markus 343: if (ai)
344: break; /* Successful connection. */
1.1 deraadt 345:
1.110 markus 346: attempt++;
347: if (attempt >= connection_attempts)
348: break;
1.38 markus 349: /* Sleep a moment before retrying. */
350: sleep(1);
351: }
1.49 markus 352:
353: freeaddrinfo(aitop);
354:
1.38 markus 355: /* Return failure if we didn't get a successful connection. */
356: if (attempt >= connection_attempts)
1.110 markus 357: return full_failure ? ECONNABORTED : ECONNREFUSED;
1.38 markus 358:
359: debug("Connection established.");
360:
1.40 markus 361: /*
362: * Set socket options. We would like the socket to disappear as soon
363: * as it has been closed for whatever reason.
364: */
365: /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.38 markus 366: linger.l_onoff = 1;
367: linger.l_linger = 5;
1.90 markus 368: setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));
369:
370: /* Set keepalives if requested. */
371: if (options.keepalives &&
372: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
373: sizeof(on)) < 0)
374: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 375:
376: /* Set the connection. */
377: packet_set_connection(sock, sock);
1.1 deraadt 378:
1.110 markus 379: return 0;
1.59 markus 380: }
381:
1.43 markus 382: /*
1.39 deraadt 383: * Waits for the server identification string, and sends our own
384: * identification string.
385: */
1.109 itojun 386: static void
1.95 itojun 387: ssh_exchange_identification(void)
1.1 deraadt 388: {
1.38 markus 389: char buf[256], remote_version[256]; /* must be same size! */
1.64 markus 390: int remote_major, remote_minor, i, mismatch;
1.38 markus 391: int connection_in = packet_get_connection_in();
392: int connection_out = packet_get_connection_out();
1.93 stevesk 393: int minor1 = PROTOCOL_MINOR_1;
1.38 markus 394:
395: /* Read other side\'s version identification. */
1.75 markus 396: for (;;) {
397: for (i = 0; i < sizeof(buf) - 1; i++) {
1.76 markus 398: int len = atomicio(read, connection_in, &buf[i], 1);
1.75 markus 399: if (len < 0)
400: fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
401: if (len != 1)
402: fatal("ssh_exchange_identification: Connection closed by remote host");
403: if (buf[i] == '\r') {
404: buf[i] = '\n';
405: buf[i + 1] = 0;
406: continue; /**XXX wait for \n */
407: }
408: if (buf[i] == '\n') {
409: buf[i + 1] = 0;
410: break;
411: }
1.38 markus 412: }
1.75 markus 413: buf[sizeof(buf) - 1] = 0;
1.76 markus 414: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 415: break;
1.75 markus 416: debug("ssh_exchange_identification: %s", buf);
1.38 markus 417: }
1.59 markus 418: server_version_string = xstrdup(buf);
1.38 markus 419:
1.40 markus 420: /*
421: * Check that the versions match. In future this might accept
422: * several versions and set appropriate flags to handle them.
423: */
1.59 markus 424: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
425: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 426: fatal("Bad remote protocol version identification: '%.100s'", buf);
427: debug("Remote protocol version %d.%d, remote software version %.100s",
428: remote_major, remote_minor, remote_version);
429:
1.59 markus 430: compat_datafellows(remote_version);
1.64 markus 431: mismatch = 0;
1.59 markus 432:
1.64 markus 433: switch(remote_major) {
434: case 1:
435: if (remote_minor == 99 &&
436: (options.protocol & SSH_PROTO_2) &&
437: !(options.protocol & SSH_PROTO_1_PREFERRED)) {
438: enable_compat20();
439: break;
440: }
441: if (!(options.protocol & SSH_PROTO_1)) {
442: mismatch = 1;
443: break;
444: }
445: if (remote_minor < 3) {
446: fatal("Remote machine has too old SSH software version.");
1.81 markus 447: } else if (remote_minor == 3 || remote_minor == 4) {
1.64 markus 448: /* We speak 1.3, too. */
449: enable_compat13();
1.81 markus 450: minor1 = 3;
1.64 markus 451: if (options.forward_agent) {
452: log("Agent forwarding disabled for protocol 1.3");
453: options.forward_agent = 0;
454: }
455: }
456: break;
457: case 2:
458: if (options.protocol & SSH_PROTO_2) {
459: enable_compat20();
460: break;
1.38 markus 461: }
1.64 markus 462: /* FALLTHROUGH */
1.68 markus 463: default:
1.64 markus 464: mismatch = 1;
465: break;
1.38 markus 466: }
1.64 markus 467: if (mismatch)
1.38 markus 468: fatal("Protocol major versions differ: %d vs. %d",
1.64 markus 469: (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
470: remote_major);
1.38 markus 471: /* Send our own protocol version identification. */
472: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.64 markus 473: compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
1.81 markus 474: compat20 ? PROTOCOL_MINOR_2 : minor1,
1.59 markus 475: SSH_VERSION);
1.45 deraadt 476: if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf))
1.38 markus 477: fatal("write: %.100s", strerror(errno));
1.59 markus 478: client_version_string = xstrdup(buf);
479: chop(client_version_string);
480: chop(server_version_string);
481: debug("Local version string %.100s", client_version_string);
1.1 deraadt 482: }
483:
1.96 markus 484: /* defaults to 'no' */
1.109 itojun 485: static int
1.112 ! markus 486: confirm(const char *prompt)
1.1 deraadt 487: {
1.38 markus 488: char buf[1024];
489: FILE *f;
490: int retval = -1;
1.96 markus 491:
492: if (options.batch_mode)
493: return 0;
1.88 markus 494: if (isatty(STDIN_FILENO))
1.38 markus 495: f = stdin;
496: else
1.95 itojun 497: f = fopen(_PATH_TTY, "rw");
1.38 markus 498: if (f == NULL)
499: return 0;
500: fflush(stdout);
501: while (1) {
502: fprintf(stderr, "%s", prompt);
503: if (fgets(buf, sizeof(buf), f) == NULL) {
504: fprintf(stderr, "\n");
505: strlcpy(buf, "no", sizeof buf);
506: }
507: /* Remove newline from response. */
508: if (strchr(buf, '\n'))
509: *strchr(buf, '\n') = 0;
510: if (strcmp(buf, "yes") == 0)
511: retval = 1;
1.79 markus 512: else if (strcmp(buf, "no") == 0)
1.38 markus 513: retval = 0;
1.79 markus 514: else
515: fprintf(stderr, "Please type 'yes' or 'no'.\n");
1.38 markus 516:
517: if (retval != -1) {
518: if (f != stdin)
519: fclose(f);
520: return retval;
521: }
1.1 deraadt 522: }
523: }
524:
1.39 deraadt 525: /*
1.108 markus 526: * check whether the supplied host key is valid, return -1 if the key
527: * is not valid. the user_hostfile will not be updated if 'readonly' is true.
1.39 deraadt 528: */
1.46 markus 529:
1.109 itojun 530: static int
1.70 markus 531: check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
1.108 markus 532: int readonly, const char *user_hostfile, const char *system_hostfile)
1.1 deraadt 533: {
1.58 markus 534: Key *file_key;
1.72 markus 535: char *type = key_type(host_key);
1.46 markus 536: char *ip = NULL;
1.100 markus 537: char hostline[1000], *hostp, *fp;
1.38 markus 538: HostStatus host_status;
539: HostStatus ip_status;
1.49 markus 540: int local = 0, host_ip_differ = 0;
541: char ntop[NI_MAXHOST];
1.88 markus 542: int host_line, ip_line;
1.85 markus 543: const char *host_file = NULL, *ip_file = NULL;
1.49 markus 544:
545: /*
546: * Force accepting of the host key for loopback/localhost. The
547: * problem is that if the home directory is NFS-mounted to multiple
548: * machines, localhost will refer to a different machine in each of
549: * them, and the user will get bogus HOST_CHANGED warnings. This
550: * essentially disables host authentication for localhost; however,
551: * this is probably not a real problem.
552: */
1.70 markus 553: /** hostaddr == 0! */
1.49 markus 554: switch (hostaddr->sa_family) {
555: case AF_INET:
1.108 markus 556: local = (ntohl(((struct sockaddr_in *)hostaddr)->
557: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
1.49 markus 558: break;
559: case AF_INET6:
1.108 markus 560: local = IN6_IS_ADDR_LOOPBACK(
561: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
1.49 markus 562: break;
563: default:
564: local = 0;
565: break;
566: }
1.111 markus 567: if (options.no_host_authentication_for_localhost == 1 && local &&
568: options.host_key_alias == NULL) {
1.88 markus 569: debug("Forcing accepting of host key for "
570: "loopback/localhost.");
1.108 markus 571: return 0;
1.49 markus 572: }
1.42 markus 573:
574: /*
1.88 markus 575: * We don't have the remote ip-address for connections
576: * using a proxy command
1.42 markus 577: */
1.84 markus 578: if (options.proxy_command == NULL) {
579: if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop),
1.86 markus 580: NULL, 0, NI_NUMERICHOST) != 0)
1.84 markus 581: fatal("check_host_key: getnameinfo failed");
582: ip = xstrdup(ntop);
583: } else {
584: ip = xstrdup("<no hostip for proxy command>");
1.86 markus 585: }
1.88 markus 586: /*
587: * Turn off check_host_ip if the connection is to localhost, via proxy
588: * command or if we don't have a hostname to compare with
589: */
590: if (options.check_host_ip &&
591: (local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
592: options.check_host_ip = 0;
1.86 markus 593:
594: /*
595: * Allow the user to record the key under a different name. This is
596: * useful for ssh tunneling over forwarded connections or if you run
597: * multiple sshd's on different ports on the same machine.
598: */
599: if (options.host_key_alias != NULL) {
600: host = options.host_key_alias;
601: debug("using hostkeyalias: %s", host);
1.84 markus 602: }
1.38 markus 603:
1.46 markus 604: /*
605: * Store the host key from the known host file in here so that we can
606: * compare it with the key for the IP address.
607: */
1.58 markus 608: file_key = key_new(host_key->type);
1.38 markus 609:
1.40 markus 610: /*
611: * Check if the host key is present in the user\'s list of known
612: * hosts or in the systemwide list.
613: */
1.85 markus 614: host_file = user_hostfile;
1.108 markus 615: host_status = check_host_in_hostfile(host_file, host, host_key,
616: file_key, &host_line);
1.85 markus 617: if (host_status == HOST_NEW) {
618: host_file = system_hostfile;
1.108 markus 619: host_status = check_host_in_hostfile(host_file, host, host_key,
620: file_key, &host_line);
1.85 markus 621: }
1.40 markus 622: /*
623: * Also perform check for the ip address, skip the check if we are
624: * localhost or the hostname was an ip address to begin with
625: */
1.88 markus 626: if (options.check_host_ip) {
1.58 markus 627: Key *ip_key = key_new(host_key->type);
1.38 markus 628:
1.85 markus 629: ip_file = user_hostfile;
1.108 markus 630: ip_status = check_host_in_hostfile(ip_file, ip, host_key,
631: ip_key, &ip_line);
1.85 markus 632: if (ip_status == HOST_NEW) {
633: ip_file = system_hostfile;
1.108 markus 634: ip_status = check_host_in_hostfile(ip_file, ip,
635: host_key, ip_key, &ip_line);
1.85 markus 636: }
1.38 markus 637: if (host_status == HOST_CHANGED &&
1.58 markus 638: (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
1.38 markus 639: host_ip_differ = 1;
640:
1.58 markus 641: key_free(ip_key);
1.38 markus 642: } else
643: ip_status = host_status;
644:
1.58 markus 645: key_free(file_key);
1.38 markus 646:
647: switch (host_status) {
648: case HOST_OK:
649: /* The host is known and the key matches. */
1.72 markus 650: debug("Host '%.200s' is known and matches the %s host key.",
651: host, type);
1.85 markus 652: debug("Found key in %s:%d", host_file, host_line);
1.88 markus 653: if (options.check_host_ip && ip_status == HOST_NEW) {
1.108 markus 654: if (readonly)
655: log("%s host key for IP address "
656: "'%.128s' not in list of known hosts.",
657: type, ip);
658: else if (!add_host_to_hostfile(user_hostfile, ip,
659: host_key))
660: log("Failed to add the %s host key for IP "
661: "address '%.128s' to the list of known "
662: "hosts (%.30s).", type, ip, user_hostfile);
1.88 markus 663: else
1.108 markus 664: log("Warning: Permanently added the %s host "
665: "key for IP address '%.128s' to the list "
666: "of known hosts.", type, ip);
1.38 markus 667: }
668: break;
669: case HOST_NEW:
1.108 markus 670: if (readonly)
671: goto fail;
1.38 markus 672: /* The host is new. */
673: if (options.strict_host_key_checking == 1) {
1.108 markus 674: /*
675: * User has requested strict host key checking. We
676: * will not add the host key automatically. The only
677: * alternative left is to abort.
678: */
679: error("No %s host key is known for %.200s and you "
680: "have requested strict checking.", type, host);
681: goto fail;
1.38 markus 682: } else if (options.strict_host_key_checking == 2) {
683: /* The default */
684: char prompt[1024];
1.100 markus 685: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1.38 markus 686: snprintf(prompt, sizeof(prompt),
1.108 markus 687: "The authenticity of host '%.200s (%s)' can't be "
688: "established.\n"
1.72 markus 689: "%s key fingerprint is %s.\n"
1.108 markus 690: "Are you sure you want to continue connecting "
691: "(yes/no)? ", host, ip, type, fp);
1.100 markus 692: xfree(fp);
1.112 ! markus 693: if (!confirm(prompt)) {
1.108 markus 694: log("Aborted by user!");
695: goto fail;
696: }
1.38 markus 697: }
1.88 markus 698: if (options.check_host_ip && ip_status == HOST_NEW) {
1.38 markus 699: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
700: hostp = hostline;
701: } else
702: hostp = host;
703:
1.108 markus 704: /*
705: * If not in strict mode, add the key automatically to the
706: * local known_hosts file.
707: */
1.70 markus 708: if (!add_host_to_hostfile(user_hostfile, hostp, host_key))
1.108 markus 709: log("Failed to add the host to the list of known "
710: "hosts (%.500s).", user_hostfile);
1.38 markus 711: else
1.108 markus 712: log("Warning: Permanently added '%.200s' (%s) to the "
713: "list of known hosts.", hostp, type);
1.38 markus 714: break;
715: case HOST_CHANGED:
716: if (options.check_host_ip && host_ip_differ) {
717: char *msg;
718: if (ip_status == HOST_NEW)
719: msg = "is unknown";
720: else if (ip_status == HOST_OK)
721: msg = "is unchanged";
722: else
723: msg = "has a different value";
724: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
725: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
726: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 727: error("The %s host key for %s has changed,", type, host);
1.38 markus 728: error("and the key for the according IP address %s", ip);
729: error("%s. This could either mean that", msg);
730: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 731: error("and its host key have changed at the same time.");
1.88 markus 732: if (ip_status != HOST_NEW)
1.85 markus 733: error("Offending key for IP in %s:%d", ip_file, ip_line);
1.38 markus 734: }
735: /* The host key has changed. */
1.100 markus 736: fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1.38 markus 737: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.47 markus 738: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1.38 markus 739: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
740: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
741: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1.72 markus 742: error("It is also possible that the %s host key has just been changed.", type);
1.87 markus 743: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1.100 markus 744: type, fp);
1.38 markus 745: error("Please contact your system administrator.");
746: error("Add correct host key in %.100s to get rid of this message.",
1.87 markus 747: user_hostfile);
1.85 markus 748: error("Offending key in %s:%d", host_file, host_line);
1.100 markus 749: xfree(fp);
1.38 markus 750:
1.40 markus 751: /*
752: * If strict host key checking is in use, the user will have
753: * to edit the key manually and we can only abort.
754: */
1.108 markus 755: if (options.strict_host_key_checking) {
756: error("%s host key for %.200s has changed and you have "
757: "requested strict checking.", type, host);
758: goto fail;
759: }
1.38 markus 760:
1.40 markus 761: /*
762: * If strict host key checking has not been requested, allow
763: * the connection but without password authentication or
764: * agent forwarding.
765: */
1.38 markus 766: if (options.password_authentication) {
1.108 markus 767: error("Password authentication is disabled to avoid "
768: "man-in-the-middle attacks.");
1.38 markus 769: options.password_authentication = 0;
770: }
771: if (options.forward_agent) {
1.108 markus 772: error("Agent forwarding is disabled to avoid "
773: "man-in-the-middle attacks.");
1.38 markus 774: options.forward_agent = 0;
1.83 markus 775: }
776: if (options.forward_x11) {
1.108 markus 777: error("X11 forwarding is disabled to avoid "
778: "man-in-the-middle attacks.");
1.83 markus 779: options.forward_x11 = 0;
780: }
1.108 markus 781: if (options.num_local_forwards > 0 ||
782: options.num_remote_forwards > 0) {
783: error("Port forwarding is disabled to avoid "
784: "man-in-the-middle attacks.");
785: options.num_local_forwards =
786: options.num_remote_forwards = 0;
1.38 markus 787: }
1.40 markus 788: /*
789: * XXX Should permit the user to change to use the new id.
790: * This could be done by converting the host key to an
791: * identifying sentence, tell that the host identifies itself
792: * by that sentence, and ask the user if he/she whishes to
793: * accept the authentication.
794: */
1.38 markus 795: break;
1.88 markus 796: }
797:
798: if (options.check_host_ip && host_status != HOST_CHANGED &&
799: ip_status == HOST_CHANGED) {
800: log("Warning: the %s host key for '%.200s' "
1.94 itojun 801: "differs from the key for the IP address '%.128s'",
1.88 markus 802: type, host, ip);
803: if (host_status == HOST_OK)
804: log("Matching host key in %s:%d", host_file, host_line);
805: log("Offending key for IP in %s:%d", ip_file, ip_line);
806: if (options.strict_host_key_checking == 1) {
1.108 markus 807: error("Exiting, you have requested strict checking.");
808: goto fail;
1.88 markus 809: } else if (options.strict_host_key_checking == 2) {
1.112 ! markus 810: if (!confirm("Are you sure you want "
! 811: "to continue connecting (yes/no)? ")) {
1.108 markus 812: log("Aborted by user!");
813: goto fail;
814: }
1.88 markus 815: }
1.38 markus 816: }
1.82 provos 817:
818: xfree(ip);
1.108 markus 819: return 0;
820:
821: fail:
822: xfree(ip);
823: return -1;
824: }
825:
826: int
827: verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
828: {
829: struct stat st;
830:
831: /* return ok if the key can be found in an old keyfile */
832: if (stat(options.system_hostfile2, &st) == 0 ||
833: stat(options.user_hostfile2, &st) == 0) {
834: if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
835: options.user_hostfile2, options.system_hostfile2) == 0)
836: return 0;
837: }
838: return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
839: options.user_hostfile, options.system_hostfile);
1.51 markus 840: }
1.70 markus 841:
1.51 markus 842: /*
843: * Starts a dialog with the server, and authenticates the current user on the
844: * server. This does not need any extra privileges. The basic connection
845: * to the server must already have been established before this is called.
846: * If login fails, this function prints an error and never returns.
847: * This function does not require super-user privileges.
848: */
849: void
1.104 markus 850: ssh_login(Key **keys, int nkeys, const char *orighost,
1.103 markus 851: struct sockaddr *hostaddr, struct passwd *pw)
1.51 markus 852: {
853: char *host, *cp;
1.70 markus 854: char *server_user, *local_user;
855:
856: local_user = xstrdup(pw->pw_name);
857: server_user = options.user ? options.user : local_user;
1.51 markus 858:
859: /* Convert the user-supplied hostname into all lowercase. */
860: host = xstrdup(orighost);
861: for (cp = host; *cp; cp++)
862: if (isupper(*cp))
863: *cp = tolower(*cp);
864:
865: /* Exchange protocol version identification strings with the server. */
866: ssh_exchange_identification();
867:
868: /* Put the connection into non-blocking mode. */
869: packet_set_nonblocking();
870:
871: /* key exchange */
872: /* authenticate user */
1.59 markus 873: if (compat20) {
874: ssh_kex2(host, hostaddr);
1.104 markus 875: ssh_userauth2(local_user, server_user, host, keys, nkeys);
1.59 markus 876: } else {
877: ssh_kex(host, hostaddr);
1.104 markus 878: ssh_userauth1(local_user, server_user, host, keys, nkeys);
1.59 markus 879: }
1.97 markus 880: }
881:
882: void
883: ssh_put_password(char *password)
884: {
885: int size;
886: char *padded;
887:
1.99 deraadt 888: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 889: packet_put_cstring(password);
1.99 deraadt 890: return;
891: }
1.97 markus 892: size = roundup(strlen(password) + 1, 32);
893: padded = xmalloc(size);
894: memset(padded, 0, size);
895: strlcpy(padded, password, size);
896: packet_put_string(padded, size);
897: memset(padded, 0, size);
898: xfree(padded);
1.1 deraadt 899: }
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